If the function $f(x)=x^4-62 x^2+ax+9$ a

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Target Exam

CUET

Subject

-- Mathematics - Section A

Chapter

Determinants

Question:

If the function $f(x)=x^4-62 x^2+ax+9$ attains its local maximum value at $x=1$, then a is equal to :

Options:

120

110

100

Correct Answer:

120

Explanation:

$f(x)=x^4-62 x^2+a x+9$

local maxima is at x = 1

$f'(x)=4 x^3-124 x+a$

so $f'(1)=0=4-124+a$ (at maxima / minima slope of function is null)

so a = 124 - 4

so a = 120